Method of and apparatus for the heat treatment of metals and alloys



March 28, 1939. A. ca. E. ROBI ETTE v 54 METHOD OF AND APPARATUS FOR THEHE AT TREATMENT OF METALS AND ,LOY Filed Jan. 20,1936

Patented Mar. 28, 1939.

METHOD OF AND APPARATUS FOR; THE HEAT 'JIREIATMEN'I 0F METALS AND ALLOYSAlfred Gordon Evans Robiette, Erdington, Birmingham, England, assignorto Birmingham Electric Furnaces Limited, ,Erdington, Birmingham,England, a British company Application January 20, 1936, Serial No.60,002 In Great Britain January 19, 1935 2Claims.

(CI. 34-24) I (Granted under the provisions of sec. 14, act

- of March 2, 1927; 357 0. G. 5)

This invention has reference to the heat-treatment of metals and alloys,and particularly to the bright-annealing of brass and other alloys thatcontain a constituent metal whichvolatilizes at annealing temperature.

It is well.known that where articles made from such alloys are producedby rolling, drawing, pressing, or other methods that involve the use ofoil or grease, it is not practically or economically possible to whollyremove the lubricant from the surfaces ofthe products before subjectingthem toheat-treatment, with the consequence that when the lubricant isdecomposed by the treatment heat, it deposits carbon on the products andcauses surface discoloration. Similarly, where the lubricant containsmoisture or other source of oxygen, such moisture or the like will bedecomposed by the treatment heat and also set up surface discoloration.

The principal object of the present invention is to provide an annealingfurnace which is adapted to perform a preliminary heating of the work inthe treatment chamber to a temperaturewhich will dry off moisture andvolatilize or vaporize oil or other lubricant, but is lower than thetemperature at which the said work is susceptible to oxidization in thepresence of moisture, and substantially lower than the annealingtemperature at which the volatile metallic constituent of the alloy mayvolatilize.

According to the present invention, this process is carried out in anannealing furnace in which a fan is employed for circulatingatmosphere-gas through the work container and through anexternally-heated passage which surrounds the said container and-isadapted to be charged with an oxidizable medium, which medium becomesoxidized preferentially to the work under treatment.

On the attached sheet of drawing, forming a part of this specification,I have illustrated a vertical sectional view of a furnace constructed inaccordance with my present invention.

The preferred form of furnace includes a fan or propeller a which willcirculate the atmosphere or gas through 'the work, especially during thepreliminary lubricant-removing treatment. It also embodies meanswhereby, during the preliminary heating, the gas-circulating passage maybe vented, or placed in communication with the outsiderair, (as, forexample, by the valve-controlled exhaust pipes c, c) to enable thedischarge or exhaust of the volatillzed or vaporized substances, whereasduring the annealing treatment, the said container may be closed, orsubstantially closed or be so controlled at the vents upon the exhaustvents may be closed, or substantially closed, to prevent or reduce theloss of at,- I

mosphere-gas during the subsequent annealing treatment.

is assisted by-the use of a body or charge of readily-oxidizable alloy(such as alloys of the same or similar constitution as the products orwork to be annealed) which is in such a physical condition, and is soarranged with respect to the work-container and heaters of the furnacethat it may readily be raised, in a given time, to a temperature higherthan that of the work-charge. Such an oxidizable charge is shown in thedrawing, marked 1, and is located and arranged in the gas circulatingsystem so that it is enabled when heated to the appropriate temperature,to take up from the circulating gas, any oxidizing substance, and/or anyvaporized lubricant that may be removed from the work-charge duringthe'annealing treatment.

Where, as in the furnace illustrated, the oxidizable charge is locatedin the gas passages outside the work-container it is heated by resistorse or the like contained in a chamber surrounding the said gas passages;the arrangement being such that when the furnace is in operation forannealing the work-charge, the oxidizable charge in theexternally-heated gas passages is maintained at a temperature ratherhigher than that of the said work charge. This enables, the oxidizablemedium to be quickly heated to its effective temperature before thework-charge is brought to annealing heat.

The oxidizable medium which becomes oxidized preferentially to thework'under treatment may consist of loosely-packed swarf or waste alloyin small pieces, or wire-mesh or the like, such as will not materiallyimpede the circulation of gas through the system. The passages in andconsisting of a metal or an alloy of metal of substantially the sameconstitution; as the metal or alloy of metal within the work-container.i

2. A process for the the cleaning and annealing of metals and alloys ofmetals comprising the step of treating said metals or alloys of metalswith heated air which has been passed in contact with an oxidizablemedium consisting of a metal oran alloy'of metal of substantiallythesame constitution as the metal or alloy of metal undergoing treatment.

ALFRED GORDON EVANS ROBIETTE.

